Process for purifying synthetic soaps



Patented Mar. 3, 1942 UNITED STATES PATENT OFFICE Q raocsss FOR l gg gi mo SYNTHETIC John .1. Owen, Baton Rouge, La., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application November 19, 1938,

' Serial No. 241,331

12 Claims.-

- aration of improved synthetic fatty acids derived from said soaps.

Synthetic fatty acids are prepared by limited oxidation of non-aromatic hydrocarbons, such as parafiinic and naphthenic petroleum oils and waxes. The soaps are obtained by neutralization of the resultinglsynthetic fatty acids with a suitable alkali, such as sodium, potassium and ammonium oxides, hydroxides and carbonates. These soaps contain colors and odors which render them objectionable for use in soap compo-' sitions of high purity, such as toilet soaps.

It has now been found that soaps of greatly improved color and purity are prepared by subjecting soaps of such synthetic acids to the action of hydrosulfites. The term hydrosulfites is used, for the purpose of this invention, to describe the' salts of the acid B28204. Suitable methods for carrying out the process of this invention are illustrated in the following example:

Example Paraffin wax derived'from petroleum is oxidized by blowing with air at about 100 to 150 C. in the presence of oxidation catalysts such as barium and manganese soaps, at atmospheric pressure, until the oxidized wax has an acid number of about 65. This oxidized product is then saponiztled by heating under pressure with a slight excess of aqueous alkali at a temperature of about 170 C. The resulting mixture is then diluted with isopropyl alcohol (to avoid emulsification) and is extracted with several volumes of petroleum naphtha to remove unsaponified materials. The rafiinate is then heated to distill off the isopropyl alcohol, which is recovered, leaving as dis-' tillation".residue an aqueous solution containing about 30% soap.

10 parts (1.25% by weight) of powdered sodium hydrosulfite (Na2S2O42H2O) were added with stirring to 800 parts of this soap solution which was maintained at 90 to 95 C. Bleaching was evidenced within a few minutes, but the treatment was continued with stirring at 90 to 95 C. for about 2 hours in order to substantially complete the treatment. The bleached soap solution was then promptly acidified with a dilute aqueous mineral acid such as sulfuric acid and the fatty acids separating from this solution as an upper layer were drawn off and washed with water several times until free of mineral acids.

Fatty acids were recovered in the same manner as above from another portion of the same soap solution without the treatment with sodium hydrosulfite. The improvement in the quality of the soaps andthe fatty acids derived therefrom is indicated by a comparison of the color of the resulting fatty acids.

Loviboud color. 6 in. cell Red Yellow Acids from bleached soap 22 135 Acids from untreated soap 528 Use of a slight excess of the hydrosulfite above that required to obtain maximum bleaching, is not objectionable. If the resulting soapsor the fatty acids derived therefrom are to be used in compositions in which the presence of small quantities of the unreacted hydrosulfite would be objectionable (because of its action on dyed materials), such effects may be avoided by adding to the bleached soap solution or the fatty acids derived therefrom, a small amount of chemicals known to react with the hydrosulfite, such as formaldehyde, or oxidizing agents, such as hydrogen peroxide, and the like. The quantities of such added chemicals should be adjusted to be just sufficient to react with or oxidize the hydrosulfite.

It is obvious that the conditions described in the above example can be varied considerably within the scope of the invention. The necessary amount of the hydrosulfite for maximum bleaching can best be obtained by actual tests with the synthetic soap solution to be treated. It will generally vary between about 0.5. and 3.0% by weight of the soap solution, or between about 1% and 10% by weight of the dry soap. Substantial improvement is obtained by conducting the treatment for a-time as short as 30 minutes or less, and it is generally desirable to conduct the treatment not much longer than about 2 hours and then to promptly stop the treatment by neutralization of any excess hydrosulfite or preferably by acidification of the reaction mixture with a dilute mineral acid. This serves both to reduce the activity of any excess hydrosulfite and to liberate the fatty acids from the soap solution undergoing treatment.

While the bleaching of natural fats and of soaps derived therefrom is ordinarily accomplished with numerous known bleaching agents, it has been found that many of such agents are not effective in improving the color of the synthetic fatty acid soaps described herein, and that the effectiveness of the hydrosulfites in this respect appears quite specific. For example, additional portions of the same soap solution used in the treatment described in the above example were treated with sodium bisulflte (NaHSOa) and with sodium thiosulfate (NazSzOa.5I-I:O). Both these known bleaching agents gave no improvement in the color of the synthetic soaps or of the acids separated therefrom.

i'he hydrosuliltes may also be added to soaps of the synthetic acids, and to compositions containing such soaps, which are to be used under conditions where the presence of small amounts of the hydrosulfites is not objectionable, or which are to be stored for some time. The hydrosulfites are added to the soaps in small amounts of about 0.5% to 3.0% by weight of the soaps, and act in such cases to improve the color and odor of the soaps during storage. The hydrosulflte may be added, for such purposes, during the finishing operation in the preparation of the soaps, for example, in the case of kettle soaps, it may be added just prior to the milling operation.

Other hydrosulfites which may be used in the treatment described above in place of the sodium salt include the alkali hydrosulfites, particularly the salts of potassium and of ammonium.

Soaps of other synthetic fatty acids may also be improved by the treatments described above, as well as the oxidized wax acid soaps as described in the example. Such synthetic fatty acids may be prepared by subjecting relatively non-aromatic liquid or solid hydrocarbons, such as crude scale wax, sweater oil, petrolatum, Diesel oils, tar products, and products obtained by distillation, extraction, cracking, hydrogenation, and destructive hydrogenation of such materials, to a limited oxidation. The oxidation is preferably conducted with the paraffin wax or other suitable initial material in liquid phase and in the presence of catalysts, such as barium and manganese soaps, using air at atmospheric or slightly elevated pressure. Other catalysts, such as the alkali metal manganates and permanganates, aqueous solutions of such catalysts and mixtures of such catalysts with basic compounds of the alkali and alkaline earth metals, such as soda ash, may also be used. The oxidation temperature is preferably maintained as low as feasible with the catalyst being used The treatment i is ordinarily conducted at temperatures of about 100 to 150 C. until a large proportion of volatile or distillable fatty acids of the molecular weight range used for soap making is obtained.

The fatty acids resulting from the treatment of the soap solutions thereof with a hydrosulflte may be separated into fractions of any desired molecular weight range by distillation, which is preferably conducted under high vacuum with the aid of steam.

The resulting fractions of the synthetic acid oxidation products may then be neutralized with suitable basic compounds, such as sodium and potassium oxides, hydroxides, or carbonates to prepare soaps of high quality by the usual soap making methods.

The present invention may also be used for the improvement of distillate fractions of the synthetic fatty acids. For example, the crude oxidation product described in the above examp16 may be saponified and the saponification products freed of unsaponified material by extraction. The remaining soap solution is then acidified with dilute mineral acid and the crude fatty acids thus liberated may be distilled, preferably under vacuum with steam, to prepare separate distillate fractions. These distillate fractions may be neutralized with aqueous alkali and the resulting soap solutions of the crude distilled synthetic fatty acids may be purified by treatment with a hydrosulfite in the manner described above. The resulting soap solutions, preferably after neutralization or removal of excess hydrosulfite, may be dried and the soaps used directly as laundry or toilet soaps. Where soaps of especially high purity are desired, these treated soap solutions are preferably acidified and the separated, purified fatty acids are neutralized with additional pure alkali, such as soda ash.

This invention is not to be limited to any examples presented herein, all of which are intended solely for purpose of illustration, but is limited only by the following claims in which it is intended to claim all novelty insofar as the prior art permit.

I claim:

1. Process for the preparation of improved synthetic fatty acid soaps comprising adding to said soaps a hydrosulfite in ampunts sumcient to improve the color and odor of the soaps.-

2. Process according to claim 1 in which the said synthetic fatty acids are obtained by limited oxidation of non-aromatic hydrocarbons.

3. Process according to claim 1 in which said hydrosulfite is a salt of an alkali metal.

4. Process for the preparation of improved synthetic fatty acid soaps comprising heating an aqueous solution of soaps of crude synthetic fatty acids with a hydrosulfite in amounts sumcient to improve the color and odor of said soaps.

5. Process for the preparation of improved synthetic fatty acids comprising heating an aqueous solution of soaps of crude synthetic fatty acids with about 0.5 to 3.0% by weight of a hydrosulfite until the color of the solution is substantially reduced, then acidifying the solution with a dilute mineral acid and separating improved synthetic fatty acids of light color therefrom.

6. Process according to claim 5 in which the said heating is conducted at a temperature of about to C. Y

'7. Process according to claim 5 in which the said heating is conducted at a temperature of about 90 to 95 C. for a time of about to2 hours.

8. Process according to claim 5 in which said hydrosulfite is sodium hydrosulfite.

9. Process for preparing synthetic fatty acids of high purity and light color comprising subjecting a petroleum wax to limited catalytic oxidation in liquid phase at a temperature of about to C., saponifying the oxidation product with aqueous alkali at a temperature of about 150 C. under pressure, separating unsaponifled matter from the saponification product by extraction, adding a small amount of sodium hydrosulfite to the resulting aqueous solution of crude soaps and heating the mixture to a temperature of about 90 to 95 C. for a time of about to 2 hours, then quickly acidifying the resulting mixture with dilute mineral acid and separating from the acidified mixture, synthetic fatty acids of improved color.

10. Improved soap composition comprising a synthetic fatty acid soap and a hydrosulnte in amount sutfic ient to improve the color and odor 12. Improved soap composition comprising a of the soap. 7 soap 01' a synthetic fatty acid prepared by oxida- 11. Improved soap composition comprising 9. tion of a petroleum wax. and sodium hydrosulflte soap of synthetic fatty acids prepared by oxidain amount sufficient to improve the color and tion of non-aromatic hydrocarbons, and a hydro- 5 odor of the soap. sulfite in amount sufficient to improve the color and odor of the soap.

JOHN J. OWEN. 

